Ignatius undoubtedly sailed from Asia Minor
to Italy, with several stops along the way to pick up other prisoners
of Rome. The Times of Ignatius by Patrick Henry Reardon
is a nice website describing the possible routes these ships often
traveled. Reardon also mentions that most of the time, these boats
were no different than a normal merchant vessel.

Sea trade was
a large part of life to the Roman people. The Romans first began
to trade across the sea when the city of Rome was growing so large
that enough grain could not be grown to handle the food demands
of the inhabitants. Therefore, the Romans quickly developed large
vessels
that could sail at speeds of 4 to 5 knots and carry hundreds
of tons of grain or other goods. The average speed of these
vessels enabled the ships to make the trip from Ostia
(the nearby port that served Rome) to Africa in two days. Although
normal trade trips could go very quickly, other sources (such
as Strabo) inform us that short trips could sometimes take months.
Although the Romans typically remained in the Mediterranean Sea
(the mare nostrum, or our sea, according to the Romans),
a few bold captains occasionally ventured up as far as Britain.
However, the Romans themselves were not as adventuresome and typically
left these voyages to other captains.

Along with the highly developed sea trade industry,
the Romans also had a strong navy. This navy was probably strongest
in the 1st Century CE, as it began to decline in the 2nd. The
navy was comprised of several types of ships, the most prevalent
being the warships. The warships were long, narrow ships controlled
completely by oars. These ships had one, two, or three rows of
oars, according to contemporary representations. These ships were
very tight and normally not very stable or seaworthy. They were
usually manned by slaves and the navy did not care if the ship
went under. The ships had a long beam extending under water that
was used to ram holes in enemy ships. Although the Romans used
this bronze covered ram, they also employed land techniques and
often boarded enemy ships by way of
a gangplank or boarding bridge. This plank had a large iron spike
at the end of it that was used to embed the plank into the enemy
ship hull. This plank was found to be quite cumbersome, however,
and was replaced by a light ladder. The navy also included several
Greek designed ships such as the Trireme
and also the Roman Quinquereme.